The present invention relates to a vehicle engine control system in which, in order to rapidly drive the fuel-injection electromagnetic valve of an internal combustion engine, a boosted high voltage is instantaneously supplied from a vehicle battery to the electromagnetic coil for driving the electromagnet valve and then valve-opening holding control is performed for a predetermined period by means of the voltage of the vehicle battery, and more particularly to the configuration of an improved voltage boosting control circuit unit.
With regard to a fuel injection control apparatus in which, for a plurality of electromagnetic coils that are provided at the respective cylinders of a multi-cylinder engine and drive the respective fuel-injection electromagnetic valves, a microprocessor that operates in response to the output of a crank angle sensor sequentially and selectively sets the respective valve opening timings and valve opening periods, there exist various methods for a voltage boosting circuit that makes it possible to perform high-frequency fuel injection and rapid opening of an electromagnetic valve. For example, according to FIG. 1 of Japanese Patent Application Publication No. 2011-241688, a high-voltage capacitor 163 for performing rapid power supply is alternately charged from first and second induction devices 161a and 161b that are on/off-driven alternately by first and second voltage boosting control circuits 160a and 160b, by way of first and second charging diodes 162a and 162b; in a period in which one of the induction devices is excited by a vehicle battery 101, electromagnetic energy accumulated in the other induction device is discharged to a high-voltage capacitor 163 so that concurrent energization by excitation currents is prevented; thus, an overcurrent from a vehicle battery is suppressed, and the heat generated in the voltage boosting circuit is dispersed. This kind of cooperative voltage boosting circuit is suitable for a fuel injection control apparatus that performs fuel injection twice or more times in one fuel supply cycle so as to raise the fuel combustion performance.
According to FIG. 2 of Japanese Patent Application Publication No. 2014-211103, in an induction device 202 that is on/off-excited by a voltage boosting opening/closing device 206 so as to charge a high-voltage capacitor 204 up to a high voltage, an induction device current Ix, which is proportional to the voltage across a current detection resistor 201A, and a detection boosted voltage Vx, which is a divided voltage of the high-voltage capacitor 204, are inputted to a voltage boosting control circuit unit 210A by way of a high-speed A/D converter provided in a calculation control circuit unit 110A; while adjusting the induction device current Ix in such a way that the adjustment is completed within a period from the present rapid excitation to the next rapid excitation, the voltage boosting control circuit unit 210A performs opening/closing control of the voltage boosting opening/closing device 206 in order to obtain a target boosted high voltage Vh that is changeably set by a microprocessor in the calculation control circuit unit 110A; as a result, it is made possible that in a voltage boosting circuit unit that generates a rapid-excitation high voltage for a fuel-injection electromagnetic coil, setting of control constants is facilitated and the opening duration of the voltage boosting opening/closing device 206 is shortened so that high-frequency charging is performed. When a pair of such voltage boosting circuits is utilized, it is also made possible to charge a common high-voltage capacitor in an asynchronous manner.